This email is just for your attention. I'm relatively new to work in a
community, so I didn't pay much attention to the readability of the
comments last email. It seems comments lie in a large patch like this is
easily to be omitted. So I cut the codes, leave codes associated with
the comments.

So now buf->indent is 1. Go to the next step, the indent is given -2
again, see what will happen.
if virBufferAdjustIndent failed to check the indent overflow, the
buf->indent will be -1,too, so it may avoid the check
(virBufferGetIndent(buf, false) != -1) and (virBufferGetIndent(buf,
true) != -1).